(a) Field of the Invention
The present invention relates to a liquid crystal display and, more specifically, to a liquid crystal display having signal lines for transmitting differential color signals.
(b) Description of the Related Art
A liquid crystal display (referred to as an LCD hereinafter) is one of the most widely used flat panel displays at present. The LCD generally includes two panels having a plurality of electrodes for generating electric field formed thereon, a liquid crystal layer interposed between the panels and polarizers for polarizing light attached to outer surfaces of the respective panels. The brightness of light from the LCD is controlled by applying voltages to the electrodes to rearrange liquid crystal molecules. A plurality of switching devices such as thin film transistors (referred to as TFTs hereinafter), connected to the electrodes, for switching the voltages applied to the electrodes are provided on one of the panels.
The LCDs include driving circuits and a controller for controlling the driving circuits to supply voltages for the electrodes through the switching devices. In general, the controller is provided external to the panels, and the driving circuits are placed either within or external to the panel. In the latter case, the driving circuits are mounted on a flexible printed circuit (FPC) film in a form of integrated circuit (IC) chips. However, in the former case, the driving circuits are either disposed on the panel in the form of IC chips, which is called COG (chip on glass) type, or incorporated with the panel by manufacturing them along with the TFTs. The latter case is generally used for the LCDs having the TFTs with polysilicon channel layers.
In the LCD, in particular, in the COG type LCD, when the signals travel from and to the controller, the driving circuits, etc. through signal lines, electromagnetic field is generated around the signal lines carrying the signals. The electromagnetic field induces interfering signals (noise) in the signal lines adjacent to the signal carrying line, thereby causing electromagnetic interference (EMI).
One of the suggested methods for reducing EMI noise is to use differential signals. Differential signals are a pair of signals having the same amplitudes but inverted phases. Instead of transmitting a signal alone, a counterpart signal having differential relationship with the original signal is generated, and the two signals are simultaneously transmitted through neighboring signal lines. The electromagnetic fields generated from the two signal lines cancel each other and EMI is decreased. However, if the two signal lines are not properly spaced, the EMI cancellation effect is decreased. Furthermore, the electromagnetic fields from the signal lines carrying two signals which are not differential interfere with each other and signal distortion is increased. Thus, it is desirable to provide an LCD having signal lines with reduced signal noise.